1. Field of the Invention
The present invention relates to a process for dimerizing vinyl olefins and more particularly relates to such a dimerization process which is fully integrated into a process for manufacturing vinyl olefins.
2. Discussion of the Prior Art
Vinylidene olefins are of commercial importance as raw materials for use in producing double tailed oxo alcohols and other functionalized derivatives, used in the manufacture of detergents, surfactants, specialty agricultural chemicals, and fuel or lubricant additives. Vinylidenes may also dimerized using a Friedel Crafts catalyst to form valuable synthetic lubricants as described in Shubkin, U.S. Pat. No. 4,172,855. Vinylidenes can be produced by dimerizing vinyl olefins. As described in Ziegler, U.S. Pat. No. 2,695,327 vinyl olefins can be dimerized using an alkyl aluminum catalyst to form vinylidenes primarily and a much smaller amount of a non-vinylidene dimer referred to herein as a xe2x80x9cdeep internal dimer.xe2x80x9d Vinylolefins can also be dimerized to form xe2x80x9cdeep internal olefin dimersxe2x80x9d primarily using a catalyst such as a Friedel Crafts catalyst (for example, BF3). The present invention is not concerned with such Friedel Crafts catalyzed dimerizations.
Numerous processes for dimerizing vinyl olefins to form vinylidenes have been disclosed. Shubkin et al., U.S. Pat. No. 4,172,855 (Oct. 30, 1979), discloses alkyl aluminum compounds as preferred catalysts for such dimerization and at a useful level of 0.1 to 10 weight percent based on the weight of the vinyl olefin and over a wide temperature range of about 50xc2x0-250xc2x0 C. or higher depending on the particular catalyst employed. In one example, approximately 85 percent of 1-octene at an initial weight of 400 grams was converted after reacting over a weekend at 120-130xc2x0 C. in the presence of 38.5 milliliters of tri-n-butyl aluminum
Lin et al., U.S. Pat. No. 4,973,788 (Nov. 27, 1990) describes a process for dimerizing a vinyl olefin monomer at a selectivity of at least 85 mole percent. This is accomplished by the use of a catalyst which consists essentially of 0.001-0.04 mole of trialkylaluminum per mole of vinyl olefin, and conducting the reaction at a temperature in the range of about 100xc2x0-140xc2x0 C. for a time sufficient to convert at least 80 mole percent of the initial vinyl olefin to a different product. The reaction rate under these conditions is quite slow, and thus a long reaction time is required. For example, it is pointed out that the time required for 90 percent conversion at 120xc2x0 C. with 0.043 mole of aluminum alkyl catalyst per mole of initial vinyl olefin is about 94 hours, and that with 0.017 mole of the catalyst per mole of initial vinyl olefin the time required at 120xc2x0 C. is about 192 hours. It is also shown in the patent that, although the reaction is faster at 172xc2x0 C. compared to 120xc2x0 C., the selectivity to vinylidene dimer is only 71 percent compared to 90 percent with the same catalyst concentration but at 120xc2x0 C. Similarly the selectivity of the conversion of the vinyl olefin to form vinylidene dimer decreased sharply as the catalyst concentration was increased above 0.043 (and up to 0.67) mole of catalyst per mole of initial vinyl olefin. The patent states that the use of larger amounts of aluminum alkyls result in the formation of unacceptably large quantities of internal olefins, both monomeric and dimeric.
In the presence of aluminum alkyl, vinyl olefins are dimerized to vinylidene olefins via the Markovnikov route. However, a competing reaction which adversely affects the yield of vinylidene olefin or the purity thereof is the isomerization of the vinylidene dimer to deep internal olefin dimer via the anti-Markovnikov route. Another undesirable competing reaction which normally tends to occur at dimerization temperatures is the isomerization of the vinyl olefin monomer to internal isomer olefin monomer via a aluminum hydride route or by other known mechanisms. Such internal olefin formation adversely affects the dimer selectivity.
Lin et al., U.S. Pat. No. 5,625,105 (Apr. 29, 1997) discloses that vinyl olefins can be dimerized to vinylidenes in good yield and in shorter reaction periods than those reported in the aforesaid Lin et al. U.S. Pat. No. 4,973,788 by using a trialkyl aluminum catalyst in the range of 0.001 to 0.05 mole of catalyst per mole of initial vinyl olefin at a temperature of 140xc2x0 to 170xc2x0 C.
Krzystowczyk et al., U.S. Pat. No. 5,663,469 (Sep. 2, 1997), discloses the formation of vinylidene olefins in good yield and high selectivity and in shorter reaction periods through the use of 0.001 to 0.5 mole of trialkyl aluminum catalyst per mole of the initial vinyl olefin, at a temperature of 100xc2x0 to 200xc2x0 C., provided that the reaction mixture is in direct contact with a nickel-containing metal alloy surface for at least one hour at a temperature above about 50xc2x0 C. and that at least one acetylenic hydrocarbon is added to the reaction mixture prior to such contact in an amount that is at least sufficient to inhibit double bond isomerization in the reaction mixture but insufficient to inhibit formation.
Thus far, prior art methods have been directed at suppressing competing double bond isomerization leading to the formation of internal isomer monomers and of deep internal olefin dimers and at the expense of relatively long reaction times. There has been no disclosure of any attempt to further reduce the length of the dimerization reaction to two hours or less and to incorporate the dimerization into a process that would better utilize the products of the aforesaid competing reactions.
It is therefore a general object of the present invention to provide an improved process for dimerizing vinyl olefins that affords such benefits.
More particularly, it is an object of the present invention to provide an improved aforesaid process that increases the rate of conversion of vinyl olefins to vinylidenes and deep internal olefins.
It is another object of the present invention to provide an improved aforesaid process that makes efficient use of unreacted vinyl olefins and products of the aforesaid competing reactions that form deep internal olefin dimers and internal isomer olefin monomers.
It is a related object of the present invention to provide an improved aforesaid process which is incorporated into a process for making vinyl olefins.
Other objects and advantages of the present invention will become apparent upon reading the following attached description and appended claims.
The present invention is an improvement in a process for manufacturing vinyl olefins containing from 4 to 30 carbon atoms, comprising: (1) reacting ethylene in a chain growth reaction in the presence of an alkyl aluminum chain growth catalyst in at least one chain growth step (2) displacing the alkyl moieties of the resulting alkyl aluminum chain growth product to form a displacement product mixture comprising the corresponding vinyl olefins formed from the alkyl moieties in at least one displacement step; (3) fractionating the displacement product mixture from at least one aforesaid displacement step to separate a liquid fraction comprising vinyl olefins containing from 4 to 30 carbon atoms; and (4) fractionating the resulting liquid fraction to separate therefrom a lower molecular weight fraction comprising the aforesaid vinyl olefins. The improvement comprises: (5) dimerizing vinyl olefins to form vinylidenes and deep internal olefins in the presence of a dimerization catalyst comprising alkyl aluminum at a initial molar ratio of alkyl aluminum to vinyl olefin of from about 0.01:1 to about 1.5:1 and at a temperature in the range of from 200xc2x0 C. to about 288xc2x0 C. for a period of time in a range of from about 30 to about 120 minutes at a selectivity for the formation of vinylidenes and deep internal olefins of at least 50 mole percent; and (6) treating the resulting dimerization product mixture by (a) combining it in its entirety with the feed to at least one aforesaid chain growth step (1) or the feed to at least one aforesaid displacement step (2); or (b) combining it in its entirety with the product mixture from at least one aforesaid chain growth step (1) or with the product mixture from at least one aforesaid displacement step (2); or (c) fractionating it to separate a light olefin fraction and a heavier fraction comprising vinylidenes and deep internal olefins which heavier fraction is then treated as in step (a) or (b); such that the resulting displacement product mixture comprises vinylidenes and deep internal olefins from the dimerization product mixture or chain growth products of such vinylidenes and deep internal olefins which are separated with the aforesaid vinyl olefins in the liquid fraction separated in step (3) and are subsequently separated as the higher molecular weight fraction from the vinyl olefins in step (4).